Reliable biomarkers are needed to identify patients with sepsis who will benefit from anti-inflammatory therapies. In addition, recent observations suggest that novel mediators (i.e., calcitonin precursors, high mobility group-1 protein) play an important role in the pathogenesis of sepsis. In order to better characterize and discover new mediators and mechanisms involved in sepsis, we are using a model of inflammation based upon the administration of endotoxin, a bacterial wall component, to normal volunteers. By administering endotoxin either intravenously or via intrabronchial instillation, we are able to study early inflammatory events that occur in the blood and in the local environment of the lung. Intravenous endotoxin results in a systemic inflammatory response that is associated with the release of acute phase cytokines and activation of inflammatory cells and endothelium. Bronchial endotoxin instillation results in a localized neutrophil influx, increased permeability to protein, and acute inflammatory mediator release in the lung. The resolution of the inflammation in the lung is associated with apoptosis of neutrophils and a mononuclear cell influx over the following 48 hours. Under protocol 92-CC-0141, the effects of endotoxin on gene expression will be studied using peripheral blood mononuclear cells and in separate studies, cells obtained with bronchoalveolar lavage from the lung. The temporal pattern of gene expression will be studied using cDNA microarrays. Spotted and oligonucleotide arrays will be performed on total mRNA extracted from these cells. These tools will be useful to study fundamental aspects of gene expression during exposure to bacterial products. It will provide one means of characterizing new mediators and mechanisms that are part of the acute phase response to bacterial products.